Resolving colliding signals

ABSTRACT

Systems and methods are disclosed herein that relate to transmitting and receiving a transmission when there is a collision between the transmission and reserved resource elements. In some embodiments, a radio access node for a cellular communications network is disclosed, wherein the radio access node comprises a transceiver, a processor, and memory storing instructions executable by the processor whereby the radio access node is operable to transmit, via the transceiver, a downlink transmission to a wireless device using one or more Physical Resource Blocks (PRBs) that comprise reserved Resource Elements (REs) by puncturing the downlink transmission at positions of the reserved REs. In some embodiments, the downlink transmission is an Enhanced Physical Downlink Control Channel (EPDCCH) transmission or a Physical Downlink Shared Channel (PDSCH) transmission. Further, in some embodiments, the reserved REs are REs utilized for one or more CSI-RSs.

RELATED APPLICATIONS

This application claims the benefit of provisional patent applicationSer. No. 62/145,375, filed Apr. 9, 2015, the disclosure of which ishereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to resolving colliding signals duringreception of a downlink transmission.

BACKGROUND

Third Generation Partnership Project (3GPP) Long Term Evolution (LTE)technology is a mobile broadband wireless communication technology inwhich transmissions from base stations (referred to as enhanced orevolved Node Bs (eNBs)) to mobile stations (referred to as UserEquipment devices (UEs)) are sent using Orthogonal Frequency DivisionMultiplexing (OFDM). OFDM splits the signal into multiple parallelsub-carriers in frequency. The basic unit of transmission in LTE is aResource Block (RB), which in its most common configuration consists of12 subcarriers and 7 OFDM symbols (one slot). A unit of one subcarrierand 1 OFDM symbol is referred to as a Resource Element (RE). Thus, an RBconsists of 84 REs. In this regard, FIG. 1 is a schematic diagramshowing LTE physical resources.

In the time domain, LTE downlink transmissions are organized into radioframes of 10 milliseconds (ms), each radio frame consisting of tenequally-sized subframes of length T_(subframe)=1 ms, as illustrated inFIG. 2. FIG. 3 is a schematic diagram of a downlink subframe. An LTEradio subframe is composed of multiple RBs in frequency with the numberof RBs determining the bandwidth of the system and two slots in time.The two RBs in a subframe that are adjacent in time are denoted as an RBpair.

The signal transmitted by the eNB in a downlink subframe (downlink beingthe link carrying transmissions from the eNB to the UE) may betransmitted from multiple antennas, and the signal may be received at aUE that has multiple antennas. The radio channel distorts thetransmitted signals from the multiple antenna ports. In order todemodulate any transmissions on the downlink, a UE relies on ReferenceSignals (RSs) that are transmitted on the downlink. These RSs and theirposition in the time-frequency grid are known to the UE and hence can beused to determine channel estimates by measuring the effect of the radiochannel on these symbols.

Machine Type Communication (MTC)

3GPP LTE has been investigated as a competitive radio access technologyfor efficient support of MTC. Lowering the cost of MTC UEs canfacilitate the implementation of the concept of the “Internet ofThings.” MTC UEs used for many applications will require low operationalpower consumption and are expected to communicate with infrequent smallburst transmissions. In addition, there is a substantial market for theMachine-to-Machine (M2M) use cases of devices deployed deep insidebuildings which would require coverage enhancement in comparison to thedefined LTE cell coverage footprint.

3GPP LTE Release 12 (Rel-12) has defined a UE Power Saving Mode (PSM)allowing long battery lifetime and a new UE category allowing reducedmodem complexity. In Release 13 (Rel-13), continued MTC work is expectedto further reduce UE cost and provide coverage enhancement. The keyelement to enable cost reduction is to introduce a reduced UE RadioFrequency (RF) bandwidth of, e.g., 1.4 Megahertz (MHz) (whichcorresponds to 6 RBs) in downlink and uplink within any systembandwidth. There is further discussion of Narrowband-IoT (NB-IoT), whichutilizes a bandwidth of 1 RB within any system bandwidth.

As a result of utilizing only a small bandwidth within the overallsystem bandwidth, these MTC devices will be unable to receive theconventional Physical Downlink Control Channel (PDCCH), which spans theentire system bandwidth within the first few symbol periods of eachdownlink subframe. As such, these MTC devices will only be able toreceive the Enhanced PDCCH (EPDCCH), which is transmitted within thedata region of the downlink subframes.

Enhanced Control Signaling in LTE-EPDCCH

Messages transmitted over the radio link to UEs can be broadlyclassified as control messages or data messages. Control messages areused to facilitate the proper operation of the system as well as theproper operation of each UE within the system. Control messages caninclude commands to control functions such as the transmitted power froma UE, signaling of RBs within which the data is to be received by the UEor transmitted from the UE, and so on.

In LTE Release 8 (Rel-8), the first one to four OFDM symbols, dependingon the configuration, in a subframe are reserved to contain such controlinformation (see FIG. 3). For normal (non-MTC) UEs of Release 11(Rel-11) or later, the UE can be configured to monitor EPDCCH inaddition to PDCCH, as specified in 3GPP Technical Specification (TS)36.211 V11.6.0 and 3GPP TS 36.213 V11.11.0. The EPDCCH was thusintroduced in Rel-11, in which 2, 4, or 8 Physical RB (PRB) pairs in thedata region are reserved to exclusively contain EPDCCH transmissions,although the one to four first symbols that may contain controlinformation to UEs of releases earlier than Rel-11 are excluded from thePRB pairs for EPDCCH transmissions.

FIG. 4 is a schematic diagram of a downlink subframe showing ten RBpairs and configuration of three EPDCCH regions of size 1 PRB pair each.Note that FIG. 4 is for conceptual illustration only, as the current LTEspecifications for EPDCCH do not support an EPDCCH region of size 1 PRBpair. The remaining PRB pairs that are not used for EPDCCH transmissionscan be used for Physical Downlink Shared Channel (PDSCH) transmissions.Thus, the EPDCCH is frequency multiplexed with PDSCH transmissionscontrary to PDCCH which is time multiplexed with PDSCH transmissions.Note also that multiplexing of PDSCH and any EPDCCH transmission withina PRB pair is not supported in LTE Rel-11.

Furthermore, two modes of EPDCCH transmission are supported. These twomodes of EPDCCH transmission are referred to as localized EPDCCHtransmission and distributed EPDCCH transmission. In distributed EPDCCHtransmission, an EPDCCH is mapped to REs in up to D PRB pairs, whereD=2, 4, or 8. In this way, frequency diversity can be achieved for theEPDCCH message. FIG. 5 is an illustration of the concept of distributedEPDCCH transmission. In particular, FIG. 5 illustrates a downlinksubframe showing four parts, or enhanced Resource Element Groups(eREGs), belonging to an EPDCCH that are mapped to multiple enhancedcontrol regions (EPDCCH regions) in an EPDCCH set to thereby achievedistributed transmission and frequency diversity.

In localized EPDCCH transmission, an EPDCCH is mapped to one or two PRBpairs only. For lower aggregation levels, only one PRB pair is used. Ifthe aggregation level of the EPDCCH is too large to fit the EPDCCH inone PRB pair, the second PRB pair is used as well. FIG. 6 is anillustration of localized EPDCCH transmission. In particular, FIG. 6illustrates a downlink subframe showing four enhanced Control ChannelElements (eCCEs) belonging to an EPDCCH, which is mapped to one of theenhanced control regions to achieve localized transmission.

To facilitate the mapping of eCCEs to physical resources, each PRB pairis divided into 16 eREGs and each eCCE is further divided into N_(eREG)^(eCCE)=4 or N_(eREG) ^(eCCE)=8 eREGs. For normal Cyclic Prefix (CP) andnormal subframes, N_(eREG) ^(eCCE)=4 unless some conditions are met, asdescribed in 3G PP TS 36.213. For extended CP and in some specialsubframes for frame structure 2 (Time Division Duplexing (TDD)),N_(eREG) ^(eCCE)=8 is used. An EPDCCH is consequently mapped to amultiple of four or eight eREGs depending on the aggregation level.

These eREGs belonging to an EPDCCH reside in either a single PRB pair(as is typical for localized transmission) or a multiple of PRB pairs(as is typical for distributed transmission). The division of a PRB pairof normal CP configuration in a normal subframe into eREGs isillustrated in FIG. 7. As illustrated, the shaded, unlabeled squaresrepresent REs that contain Demodulation Reference Signals (DMRSs). Eachlabelled square, or tile, is a RE in which the number corresponds to theeREG to which the RE belongs. The squares labelled with the same number,or index, belong to the same eREG, which is indexed with the number. Forexample, the REs labelled “0” correspond to the REs belonging to theeREG indexed with 0.

The EPDCCH uses DMRS, for demodulation, which is shown in 7. There are24 REs reserved for DMRS per PRB pair. For distributed EPDCCH, there aretwo DMRS antenna ports in each PRB pair, for normal CP, known as antennaports 107 and 109. These two antenna ports are used for all distributedEPDCCH messages in the PRB pair and provide two-fold antenna diversity(if the eNB chooses to transmit each port from a separate antenna, whichis an implementation choice). For localized EPDCCH, there are up to fourantenna ports 107-110, and each antenna port is used by one EPDCCHmessage only in that PRB pair.

Port 107 uses 12 REs out of the 24 REs in the PRB pair, while port 109uses the other 12 REs. Hence, the DMRS REs belonging to ports 107 and109 are time and frequency multiplexed in the PRB pair. On the otherhand, ports 107 and 108 (and also ports 109 and 110) use the same REsbut are code multiplexed by applying an Orthogonal Cover Code (OCC) ontop of 4 REs on the same subcarrier. The OCC used for ports 107-110 tocreate orthogonality are shown in the table below from 3GPP TS 36.211.

TABLE 6.10.3A.2-1 The sequence w _(p) ^((i)) for normal cyclic prefixAntenna port p [w _(p)(0) w _(p)(1) w _(p)(2) w _(p)(3)] 107 [+1 +1 +1+1] 108 [+1 −1 +1 −1] 109 [+1 +1 +1 +1] 110 [+1 −1 +1 −1]For extended CP, only code multiplexed DMRS is used, and the length oftwo OCCs for ports 107 and 108 are given in the table below from 3GPP TS36.211.

TABLE 6.10.3A.2-2 The sequence w _(p) ^((i)) for extended cyclic prefixAntenna port p [w _(p)(0) w _(p)(1)] 107 [+1 +1] 108 [−1 +1]

When receiving the distributed EPDCCH, the UE estimates the channel ineach DMRS RE, and then the UE uses the OCC within each subcarrier andthe corresponding three subcarriers within the PRB pair to obtain thechannel estimate for antenna ports 107 and 109, respectively. Thesechannel estimates are then used when demodulating the EPDCCH.

Demodulation of PDSCH

For PDSCH, the antenna port (port 7-15) to use for demodulation of DMRSbased transmission modes (9 or 10) is included in the Downlink ControlInformation (DCI) message that schedules the PDSCH. The DMRS antennaports 7-15 for PDSCH use the same REs in the PRB pair as the DMRS ports107, 109 for EPDCCH. Hence, for a rank 1 transmission, which is what anMTC device will use, port 7 will be used for PDSCH demodulation, and thecorresponding REs are shown in FIG. 8.

For PDSCH DMRS ports, the following OCCs are applied (the followingtable is a reproduction of Table 6.10.3.2-1 from 3GPP TS 36.211):

Table 6.10.3.2-1 The sequence w _(p) ^((i)) for normal cyclic prefixAntenna port p [w _(p)(0) w _(p)(1) w _(p)(2) w _(p)(3)]  7 [+1 +1 +1+1]  8 [+1 −1 +1 −1]  9 [+1 +1 +1 +1] 10 [+1 −1 +1 −1] 11 [+1 +1 −1 −1]12 [−1 −1 +1 +1] 13 [+1 −1 −1 +1] 14 [−1 +1 +1 −1]

SUMMARY

Systems and methods are disclosed herein that relate to transmitting andreceiving a transmission when there is a collision between thetransmission and reserved Resource Elements (REs). In some embodiments,a radio access node for a cellular communications network is disclosed,wherein the radio access node comprises a transceiver, a processor, andmemory storing instructions executable by the processor whereby theradio access node is operable to transmit, via the transceiver, adownlink transmission to a wireless device using one or more PhysicalResource Blocks (PRBs) that comprise reserved REs by puncturing thedownlink transmission at positions of the reserved REs. In someembodiments, the downlink transmission is an Enhanced Physical DownlinkControl Channel (EPDCCH) transmission or a Physical Downlink SharedChannel (PDSCH) transmission.

In some embodiments, the downlink transmission is an EPDCCHtransmission. Further, in some embodiments, the reserved REs are REsutilized for one or more Channel State Information Reference Signals(CSI-RSs).

In some embodiments, the downlink transmission is a PDSCH transmission.Further, in some embodiments, the reserved REs are REs utilized for oneor more CSI-RSs.

Embodiments of a method of operation of a radio access node in acellular communications network are also disclosed. In some embodiments,the method of operation of the radio access node comprises transmittinga downlink transmission to a wireless device using one or more PRBs thatcomprise reserved REs by puncturing the downlink transmission atpositions of the reserved REs. In some embodiments, the downlinktransmission is an EPDCCH transmission or a PDSCH transmission.

In some embodiments, the downlink transmission is an EPDCCHtransmission. Further, in some embodiments, the reserved REs are REsutilized for one or more CSI-RSs.

In some embodiments, the downlink transmission is a PDSCH transmission.Further, in some embodiments, the reserved REs are REs utilized for oneor more CSI-RSs.

In some embodiments, a radio access node for a cellular communicationsnetwork is adapted to perform the method of operation of a radio accessnode according to any of the embodiments disclosed herein.

In some embodiments, a radio access node for a cellular communicationsnetwork comprises a transmit module operable to transmit a downlinktransmission to a wireless device using one or more PRBs that comprisereserved REs by puncturing the downlink transmission at positions of thereserved REs. In some embodiments, the downlink transmission is anEPDCCH transmission or a PDSCH transmission.

Embodiments of a non-transitory computer-readable medium are disclosed,wherein the non-transitory computer-readable medium stores softwareinstructions that when executed by one or more processors of a radioaccess node cause the radio access node to transmit a downlinktransmission to a wireless device using one or more PRBs that comprisereserved REs by puncturing the downlink transmission at positions of thereserved REs. In some embodiments, the downlink transmission is anEPDCCH transmission or a PDSCH transmission.

Embodiments of a computer program are disclosed, wherein the computerprogram comprises instructions which, when executed on at least oneprocessor, cause the at least one processor to carry out the method ofoperation of a radio access node according to any of the embodimentsdisclosed herein. Embodiments of a carrier are also disclosed, whereinthe carrier contains the aforementioned computer program and is one ofan electronic signal, an optical signal, a radio signal, or a computerreadable storage medium.

Embodiments of a wireless device enabled to operate in a cellularcommunications network are also disclosed. In some embodiments, thewireless device comprises a transceiver, a processor, and memory storinginstructions executable by the processor whereby the wireless device isoperable to receive, via the transceiver, a downlink transmission from aradio access node on one or more PRBs based on an assumption by thewireless device that the downlink transmission on the one or more PRBsis punctured by reserved REs if any. In some embodiments, the downlinktransmission is an EPDCCH transmission or a PDSCH transmission.

In some embodiments, the downlink transmission is an EPDCCHtransmission. Further, in some embodiments, the reserved REs are REsutilized for one or more CSI-RSs.

In some embodiments, the downlink transmission is a PDSCH transmission.Further, in some embodiments, the reserved REs are REs utilized for oneor more CSI-RSs.

Embodiments of a method of operation of a wireless device in a cellularcommunications network are also disclosed. In some embodiments, themethod of operation of the wireless device comprises receiving adownlink transmission from a radio access node on one or more PRBs basedon an assumption by the wireless device that the downlink transmissionon the one or more PRBs is punctured by reserved REs if any. In someembodiments, the downlink transmission is an EPDCCH transmission or aPDSCH transmission.

In some embodiments, the downlink transmission is an EPDCCHtransmission. Further, in some embodiments, the reserved REs are REsutilized for one or more CSI-RSs.

In some embodiments, the downlink transmission is a PDSCH transmission.Further, in some embodiments, the reserved REs are REs utilized for oneor more CSI-RSs.

In some embodiments, a wireless device enabled to operate in a cellularcommunications network is adapted to perform the method of operation ofa wireless device according to any of the embodiments disclosed herein.

In some embodiments, a wireless device enabled to operate in a cellularcommunications network comprises a receive module operable to receive adownlink transmission from a radio access node on one or more PRBs basedon an assumption by the wireless device that the downlink transmissionon the one or more PRBs are punctured by reserved REs if any. In someembodiments, the downlink transmission is an EPDCCH transmission or aPDSCH transmission.

Embodiments of a non-transitory computer-readable medium are alsodisclosed, wherein the non-transitory computer-readable medium storessoftware instructions that when executed by one or more processors of awireless device cause the wireless device to receive a downlinktransmission from a radio access node on one or more PRBs based on anassumption by the wireless device that the downlink transmission on theone or more PRBs are punctured by reserved REs if any. In someembodiments, the downlink transmission is an EPDCCH transmission or aPDSCH transmission.

Embodiments of a computer program are also disclosed, wherein thecomputer program comprises instructions which, when executed on at leastone processor, cause the at least one processor to carry out the methodof operation of a wireless device according to any of the embodimentsdisclosed herein. Further, embodiments of a carrier containing theaforementioned computer program are also disclosed, wherein the carrieris one of an electronic signal, an optical signal, a radio signal, or acomputer readable storage medium.

In other embodiments, a method of operation of a wireless device in acellular communications network comprises obtaining an indicator that isindicative of whether reserved REs are present in a subframe in which adownlink transmission is transmitted from a radio access node to thewireless device. The downlink transmission is an EPDCCH transmission ora PDSCH transmission. The method further comprises determining whetherreserved REs are present in the subframe based on the indicator and,upon determining that reserved REs are present in the subframe,attempting reception of the downlink transmission based on an assumptionthat reserved REs are present in the subframe.

In some embodiments, the method further comprises, upon determining thatreserved REs are not present in the subframe, attempting reception ofthe downlink transmission based on an assumption that reserved REs arenot present in the subframe.

In some embodiments, the downlink transmission is an EPDCCHtransmission. Further, in some embodiments, the reserved REs are REsutilized for one or more CSI-RSs.

In some embodiments, the downlink transmission is a PDSCH transmission.Further, in some embodiments, the reserved REs are REs utilized for oneor more CSI-RSs.

In some embodiments, obtaining the indicator comprises detecting anOrthogonal Cover Code (OCC) indicator in the subframe that is indicativeof whether reserved REs are present in the subframe. Further, in someembodiments, the OCC indicator is an OCC utilized for a DemodulationReference Signal (DMRS) antenna port within the subframe. In someembodiments, the OCC indicator is further indicative of which of aplurality of predefined sets of reserved REs is present in the subframe.In some embodiments, positions of the reserved REs within the subframeare predefined.

In some embodiments, obtaining the indicator comprises receiving andstoring a configuration of reserved REs in multiple subframes, includingthe subframe, from received system information. The configuration ofreserved REs in the multiple subframes comprises the indicator that isindicative of whether reserved REs are present in the subframe. Further,in some embodiments, the wireless device is a Machine Type Communication(MTC) device, and the received system information is a MTC MasterInformation Block (MTC-MIB). In other embodiments, the wireless deviceis a MTC device, and the received system information is a MTC SecondaryInformation Block (MTC-SIB).

In some embodiments, attempting reception of the downlink transmissionbased on an assumption that reserved REs are present in the subframecomprises de-mapping a plurality of REs corresponding to the downlinktransmission from one or more Physical Resource Blocks (PRBs) in thesubframe.

In some embodiments, attempting reception of the downlink transmissionbased on an assumption that reserved REs are present in the subframecomprises ignoring the reserved REs during reception of the downlinktransmission.

Embodiments of a wireless device enabled to operate in a cellularcommunications network are also disclosed. In some embodiments, thewireless device comprises a transceiver, a processor, and memory storinginstructions executable by the processor whereby the wireless device isoperable to: obtain an indicator that is indicative of whether reservedREs are present in a subframe in which a downlink transmission istransmitted from a radio access node to the wireless device; determinewhether reserved REs are present in the subframe based on the indicator;and, upon determining that reserved REs are present in the subframe,attempt reception of the downlink transmission based on an assumptionthat reserved REs are present in the subframe. In some embodiments, thedownlink transmission is an EPDCCH transmission or a PDSCH transmission.

In some embodiments, in order to obtain the indicator, the wirelessdevice is further operable to detect an OCC indicator in the subframethat is indicative of whether reserved REs are present in the subframe.

In some embodiments, in order to obtain the indicator, the wirelessdevice is further operable to receive and store a configuration ofreserved REs in multiple subframes, including the subframe, fromreceived system information. The configuration of reserved REs in themultiple subframes comprising the indicator that is indicative ofwhether reserved REs are present in the subframe.

In some embodiments, a wireless device enabled to operate in a cellularcommunications network is adapted to perform the method of operation ofa wireless device according to any of the embodiments disclosed herein.

In some embodiments, a wireless device enabled to operate in a cellularcommunications network comprises an obtaining module operable to obtainan indicator that is indicative of whether reserved REs are present in asubframe in which a downlink transmission is transmitted from a radioaccess node to the wireless device, a determining module operable todetermine whether reserved REs are present in the subframe based on theindicator, and a reception module operable to, upon determining thatreserved REs are present in the subframe, attempt reception of thedownlink transmission based on an assumption that reserved REs arepresent in the subframe. In some embodiments, the downlink transmissionis an EPDCCH transmission or a PDSCH transmission.

Embodiments of a non-transitory computer-readable medium are alsodisclosed, wherein the non-transitory computer-readable medium storessoftware instructions that when executed by one or more processors of awireless device cause the wireless device to: obtain an indicator thatis indicative of whether reserved REs are present in a subframe in whicha downlink transmission is transmitted from a radio access node to thewireless device in a subframe, determine whether reserved REs arepresent in the subframe based on the indicator, and upon determiningthat reserved REs are present in the subframe, attempt reception of thedownlink transmission based on an assumption that reserved REs arepresent in the subframe. In some embodiments, the downlink transmissionis an EPDCCH transmission or a PDSCH transmission.

Embodiments of a computer program are also disclosed, wherein thecomputer program comprises instructions which, when executed on at leastone processor, cause the at least one processor to carry out the methodof operation of a wireless device according to any of the embodimentsdisclosed herein. Further, embodiments of a carrier containing theaforementioned computer program are also disclosed, wherein the carrieris one of an electronic signal, an optical signal, a radio signal, or acomputer readable storage medium.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the embodiments in association withthe accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the disclosure, andtogether with the description serve to explain the principles of thedisclosure.

FIG. 1 is a schematic diagram showing Long Term Evolution (LTE) physicalresources;

FIG. 2 is a schematic diagram of an LTE radio frame;

FIG. 3 is a schematic diagram of a downlink subframe;

FIG. 4 is a schematic diagram of a downlink subframe showing tenResource Block (RB) pairs and configuration of three enhanced PhysicalDownlink Control Channel (EPDCCH) regions of size 1 Physical RB (PRB)pair each;

FIG. 5 is an illustration of the concept of distributed EPDCCHtransmission;

FIG. 6 is an illustration of localized EPDCCH transmission;

FIG. 7 illustrates the division of a PRB pair of normal Cyclic Prefix(CP) configuration in a normal subframe into enhanced Resource ElementGroups (eREGs);

FIG. 8 illustrates the Resource Elements (REs) used for PhysicalDownlink Shared Channel (PDSCH) demodulation for a rank 1 transmission;

FIG. 9 illustrates one example of a cellular communications network inwhich embodiments of the present disclosure may be implemented;

FIG. 10 illustrates the operation of a base station and a wirelessdevice to enable reception of an EPDCCH transmission or a PDSCHtransmission by the wireless device according to some embodiments of thepresent disclosure;

FIG. 11 illustrates the operation of the base station and the wirelessdevice according to some embodiments in which the base station transmitsa downlink transmission (e.g., an EPDCCH transmission or a PDSCHtransmission) to the wireless device along with an Orthogonal Cover Code(OCC) indicator that indicates whether reserved REs are presentaccording to some embodiments of the present disclosure;

FIG. 12 is flow chart that illustrates the operation of the wirelessdevice with respect to receiving and using an OCC indicator (alsoreferred to herein as an OCC-based indication) according to someembodiments of the present disclosure;

FIG. 13 illustrates the operation of the base station and the wirelessdevice to provide and utilize broadcast signaling for indicating thepresence of reserved REs according to some embodiments of the presentdisclosure;

FIG. 14 is a flow chart that illustrates the operation of the wirelessdevice in more detail according to some embodiments of the presentdisclosure;

FIG. 15 is a block diagram of a base station, or more generally a radioaccess node, according to some embodiments of the present disclosure;

FIG. 16 is a block diagram of a virtualized embodiment of a radio accessnode according to some embodiments of the present disclosure;

FIG. 17 is a block diagram of a base station, or more generally a radioaccess node, according to some other embodiments of the presentdisclosure;

FIG. 18 is a block diagram of a wireless device according to someembodiments of the present disclosure; and

FIG. 19 is a block diagram of a wireless device according to some otherembodiments of the present disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent information to enable thoseskilled in the art to practice the embodiments and illustrate the bestmode of practicing the embodiments. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the disclosure and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

Radio Node: As used herein, a “radio node” is either a radio access nodeor a wireless device.

Radio Access Node: As used herein, a “radio access node” is any node ina radio access network of a cellular communications network thatoperates to wirelessly transmit and/or receive signals. Some examples ofa radio access node include, but are not limited to, a base station(e.g., an enhanced or evolved Node B (eNB) in a Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) network), ahigh-power or macro base station, a low-power base station (e.g., amicro base station, a pico base station, a home eNB, or the like), and arelay node.

Core Network Node: As used herein, a “core network node” is any type ofnode in a Core Network (CN). Some examples of a CN node include, e.g., aMobility Management Entity (MME), a Packet Data Network (PDN) Gateway(P-GW), a Service Capability Exposure Function (SCEF), or the like.

Wireless Device: As used herein, a “wireless device” is any type ofdevice that has access to (i.e., is served by) a cellular communicationsnetwork by wirelessly transmitting and/or receiving signals to a radioaccess node(s). Some examples of a wireless device include, but are notlimited to, a User Equipment device (UE) in a 3GPP LTE network and aMachine Type Communication (MTC) device.

Network Node: As used herein, a “network node” is any node that iseither part of the radio access network or the CN of a cellularcommunications network/system.

Note that the description given herein focuses on a 3GPP cellularcommunications system and, as such, 3GPP LTE terminology or terminologysimilar to 3GPP LTE terminology is oftentimes used. However, theconcepts disclosed herein are not limited to a 3GPP system.

Note that, in the description herein, reference may be made to the term“cell;” however, particularly with respect to Fifth Generation (5G)concepts, beams may be used instead of cells and, as such, it isimportant to note that the concepts described herein are equallyapplicable to both cells and beams.

In LTE, a physical control or data channel, such as a Physical DownlinkShared Channel (PDSCH) or Enhanced Physical Downlink Control Channel(EPDCCH), is mapped to Resource Elements (REs) for transmission. SomeREs contains other signals such as Reference Signals (RS), and, in thosecases, the data is not mapped to those REs. The presence and location ofthe RSs are, for some RS types such as Channel State InformationReference Signal (CSI-RS), signaled to each UE in a dedicatedconfiguration message.

A problem then occurs when attempting to receive a physical control ordata channel, such as an EPDCCH or a PDSCH containing a paging message,a system information message (e.g., a Secondary Information Block(SIB)), a Multimedia Broadcast/Multicast Service (MBMS) schedulingmessage, or a Random Access Response (RAR) message, before thelocations, or positions, of these UE specific RSs, such as CSI-RSs, havebeen indicated to the UE. For instance, a UE should be able to receiveRAR messages when accessing the cell without being configured with thelocation of the CSI-RS beforehand.

This problem is particularly severe when a PDSCH containing, e.g., RARsare repeated over many, sometimes tens or hundreds, of subframes, sincesome subframes contain UE specific RSs (configured to other UEs) andsome subframes do not. This repeated PDSCH is typical for extendedcoverage operation of LTE, which is under discussion for LTE Release 13(Rel-13).

One solution is to puncture the PDSCH with CSI-RS without the UE knowingabout the puncturing. In other words, the UE does not know about thepuncturing and, as such, assumes that there are no CSI-RSs within thePRBs on which the PDSCH is received. The UE may still be able to decodethe PDSCH but with a loss in performance and coverage. In some cases, ifCSI-RS puncturing is severe, the PDSCH message may be impossible todecode, which is a further problem.

Embodiments are also disclosed in which various means for providinginformation to the receiving UE to enable the UE to earlier detectwhether the subframe contains reserved REs or not. As used herein, theterm “reserved RE” refers to an RE that is occupied by, for instance,CSI-RS.

In some embodiments, the transmitter (i.e., the transmitter of the radioaccess node such as, e.g., the eNB) modifies the Demodulation ReferenceSignal (DMRS) of the antenna ports used for the demodulation of themessage. For instance, an antenna port does not only correspond to oneOrthogonal Cover Code (OCC) but to two OCCs. If the CSI-RS is notpresent in the subframe, then the first OCC is used; otherwise, thesecond OCC is used for this antenna port. The UE can then in the channelestimation process detect whether the first or second OCC wastransmitted for this antenna port. Then, the UE knows whether CSI-RS(i.e., reserved REs) are present in the subframe or not and can de-mapthe message from the REs in the Physical Resource Block (PRB) pair in acorrect way. Hence, in some embodiments, per-subframe, implicitindication of CSI-RS presence is provided at each UE in a UE-specificmanner.

In some other embodiments, broadcast configuration information aboutreserved REs is broadcast to UEs. Hence, in some embodiments, asemi-static, explicit indication of CSI-RS is provided to multiple UEs(e.g., MTC UEs) in a shared manner.

Aspects of the embodiments of the present disclosure are directed to amethod performed at a UE, where the UE comprises a transceiver and ahardware processor. In some embodiments, the UE can receive informationabout reserved REs. The UE can determine whether a subframe includes areserved RE. The UE can attempt reception of a Physical Downlink ControlChannel (PDCCH) on the subframe based on whether the subframe includes areserved RE.

Advantages of the present disclosure are readily identifiable to thoseof ordinary skill in the art. Among the advantages are improvements inthe reception performance of messages in situations where there may beambiguity between an eNB and a UE of which REs are reserved for othersignals such as CSI-RSs.

This disclosure addresses the problem of a UE, particularly a MTC UE,being able to receive a downlink transmission (e.g., EPDCCH or PDSCHtransmission) when transmitting the downlink transmission from the eNBto the UE when the receiver (i.e., the UE) is not aware of the presenceand location of reserved REs in the PRB pair. Of particular interest iswhen such a message is repeated over many subframes, since there will bea collision in some of these subframes only (as not all subframescontain reserved REs). When transmitting such a message in only a singlesubframe, the problem may be avoided by the scheduler at the eNB bysimply avoiding subframes containing reserved REs of which the receivingUE is unaware. This approach, used in legacy systems, cannot be usedwhen the message is repeated over many subframes.

Typical applications include transmitting paging, system information,random access response, and/or EPDCCH containing a common search space(which needs to be received prior to receiving system information in aPDSCH message, for instance). A common occurrence of a reserved RE isthe transmission of CSI-RS, which is specifically configured bydedicated Radio Resource Control (RRC) signaling. Prior to receivingthis configuration, the eNB has to transmit paging, RAR, etc. insubframes without CSI-RS, or the message needs to be punctured by CSI-RSleading to degraded performance.

Puncturing means that the PDSCH or the EPDCCH is first mapped to REs andthen the RE reserved for, e.g., CSI-RS are replaced by the CSI-RSsignals. Hence, the UE will “believe” that all REs are used for PDSCHbut in fact some of them contain CSI-RS. As the UE is unaware of this,the UE will treat whatever is transmitted in these reserved REs as PDSCHREs and performance degrades.

If the UE is aware of the CSI-RS presence (or any other reserved RE),then the CSI-RS can be mapped to the RE first and then the PDSCH orEPDCCH is mapped to the RE around these CSI-RS REs. This is called ratematching around CSI-RS REs.

In some embodiments, the present disclosure provides systems and methodsthat avoid the losses associated with puncturing or rate matching. Insome embodiments, whether or not a subframe contains reserved REs isdynamically (per subframe) indicated to the UE, prior to thedemodulation. In some embodiments, the way to do this is to encodeinformation in the DMRS used to demodulate the message. The UE can thentest hypotheses of the DMRS and detect one of them to determine thepresence or absence of reserved REs.

In this regard, FIG. 9 illustrates one example of a cellularcommunications network 10 in which embodiments of the present disclosuremay be implemented. In this example, the cellular communications network10 is a 3GPP LTE network and, as such, LTE terminology is sometimesused; however, the concepts disclosed herein are not limited to LTE.

As illustrated, the cellular communication network 10 includes a RadioAccess Network (RAN) 12 that includes radio access nodes such as basestations 14 (eNBs in LTE terminology) that serve corresponding cells 16.The base stations 14 provide radio access to wireless devices 18 (e.g.,UEs, MTC UEs, etc.) within the coverage areas of the cells 16. The basestations 14 are communicatively coupled via abase-station-to-base-station interface (referred to as an X2 interfacein LTE) and are also communicatively coupled to a core network 20 viarespective core network interfaces (referred to as S1 interfaces inLTE). The core network 20 includes a number of core network nodesincluding, e.g., one or more MMEs 22, one or more Serving Gateways(S-GWs) 24, and one or more P-GWs 26.

As described above, a problem arises when the wireless device 18 is aMTC device or other device that is unable to receive the conventionalPDCCH (e.g., due to only receiving a small portion of the total systembandwidth). In particular, when attempting to receive an EPDCCH or PDSCHtransmission, the wireless device 18 may not be aware of whether thePRBs on which reception is being attempted include reserved REs such as,e.g., REs used to transmit CSI-RS. If rate-matching is used at the basestation 14 when transmitting the EPDCCH or PDSCH transmission, then thewireless device 18 will not be able to accurately de-map the REs usedfor the EPDCCH transmission or PDSCH transmission when reserved REs arepresent in the PRBs because the wireless device 18 is unaware of thereserved REs.

FIG. 10 illustrates the operation of the base station 14 and thewireless device 18 to enable reception of an EPDCCH transmission or aPDSCH transmission by the wireless device 18 according to someembodiments of the present disclosure. In some embodiments, the wirelessdevice 18 is unaware of (i.e., does not have knowledge of) theconfiguration of reserved REs (e.g., REs used for CSI-RS) in therespective REs within the subframe. As illustrated, the base station 14transmits an EPDCCH transmission or a PDSCH transmission (or potentiallyboth) to the wireless device 18 using PRBs that include reserved REs(e.g., REs used for CSI-RS) by puncturing the EPDCCH transmission or thePDSCH transmission (e.g., without the wireless device 18 havingknowledge of the puncturing) (step 100). Thus, when transmitting thedownlink transmission (i.e., the EPDCCH transmission or the PDSCHtransmission), the base station 14 first maps the REs for the downlinktransmission to the PRBs and then maps, or overwrites, the reserved REswith the appropriate symbols (e.g., CSI-RS symbols). In someembodiments, at this point, the wireless device 18 is unaware of thepuncturing.

The wireless device 18 receives (i.e., attempts to receive) the EPDCCHtransmission or the PDSCH transmission in the subframe assuming that theEPDCCH transmission or the PDSCH transmission is punctured by reservedREs, if any (step 102). In other words, the wireless device 18 does nothave knowledge of the presence of the reserved REs within the PRBs onwhich the wireless device 18 is attempting to receive the EPDCCHtransmission or the PDSCH transmission and, as such, the wireless device18 attempts to receive the EPDCCH transmission or the PDSCH transmissionassuming that, if any reserved REs are present, the EPDCCH transmissionor the PDSCH transmission is punctured by the reserved REs. In otherwords, this can be thought of as the wireless device 18 attempting toreceive the EPDCCH transmission or the PDSCH transmission assuming that(as if) no reserved REs are present. The presence of the unknownreserved REs may degrade the ability of the wireless device 18 tosuccessfully receive the EPDCCH transmission or the PDSCH transmission;however, this may be overcome at the base station 14 by, for example,increasing the number of repetitions (in the case of a MTC device wherethe EPDCCH transmission or the PDSCH transmission is repeated many timesto provide enhanced coverage) Alternatively, the network can also reducethe code rate and thus improve the chance to decode the message at thereceiver by increasing the number of aggregated eCCEs for the message(i.e., increasing the aggregation level) in case the network anticipatesthat the message will be punctured by REs unknown to the receiver.

In the embodiment of FIG. 10, the wireless device 18 may not be aware ofthe presence of the reserved REs. Embodiments are also disclosed hereinfor signaling the presence of reserved REs to the wireless device 18. Insome embodiments, signaling is provided in the presence of reserved REs.More specifically, in some embodiments, for distributed EPDCCH, thenormal OCC is used for ports 107 and 109 when there are no reserved REs(e.g., CSI-RS REs) in the subframe and, alternatively, a modified OCC isused when there are reserved REs present in the subframe. An example isprovided in the table below. It should be noted that, in this example,it can equivalently be interpreted as ports 108/110 are used instead ofports 107/109 when there are reserved REs present in the subframe sincethe modified OCC matches these alternative antenna ports.

TABLE 1 OCC indicates presence of reserved RE in the subframe fordistributed EPDCCH Antenna port p [w _(p)(0) w _(p)(1) [w _(p)(0) w_(p)(1) w _(p)(2) w _(p)(3)] w _(p)(2) w _(p)(3)] Reserved RE present insubframe? No Yes 107 [+1 +1 +1 +1] [+1 −1 +1 −1] 109 [+1 +1 +1 +1] [+1−1 +1 −1]Note that other OCCs than given by this example are also possible. It isalso possible that multiple OCCs are used to indicate a different numberof different sets of reserved REs such that it is possible to signalthat, e.g., a few reserved REs are present in this subframe or that allREs that can potentially be reserved are actually reserved in thissubframe.

In some further embodiments, the REs that belong to the set of reservedREs are given by specifications. For instance, in some embodiments, whendetecting that a subframe has CSI-RS present, the wireless device 18assumes that all possible CSI-RS resources (40 REs) are reserved.Alternatively, in some embodiments, the wireless device 18 is configured(e.g., at some time prior to receiving the OCC indicator) with theinterpretation of “reserved RE” by receiving a system informationbroadcast message, or by reading information in the SubscriberIdentification Module (SIM). In this case, it is possible that only asubset of the potential 40 REs for CSI-RS are treated as reserved REs,thus providing more accurate information than always assuming themaximum number of reserved REs.

For extended Cyclic Prefix (CP) and normal subframes, the OCC length,which currently is two, can be increased to four and the same method asfor normal CP can be used.

In some other embodiments, OCCs can be applied for PDSCH and rank 1transmission, as is used for low complexity MTC and coverage extensionapplications. For example, only port 7 is used for the PDSCH. In thiscase, the normal OCC for port 7 is [+1 +1 +1 +1]. Hence, the presence ofreserved REs can be indicated by modifying the OCC for port 7 to [+1 −1+1 −1] or any OCC that is orthogonal to the normal OCC for this port.Also, in this case, it is possible to indicate one out of multiple setsof reserved REs since there are 4 orthogonal OCCs of length 4 and eachcan be associated with a unique set of reserved REs. Identifyingreserved REs is desirable for those messages that are sent before RRCconfiguration is received by the wireless device 18. These messagesinclude SIB, RAR, and paging.

The OCC-based method has the benefit of no signaling overhead anddynamic subframe-by-subframe indication. One variation is to combine anOCC-based indication with the broadcast-based indication. For example,the broadcast-based indication provides a reserved RE pattern, while theOCC-based method indicates if the reserved RE is present or not in thecurrent subframe.

In some further embodiments for localized EPDCCH, one of these antennaports may, according to 3GPP Technical Specification (TS) 36.211 V11.6.0and 3GPP TS 36.213 V11.11.0, be used for demodulation of an EPDCCHmessage in the PRB pair. Which antenna port to use depends on whichenhanced Control Channel Element (eCCE) is used for the EPDCCH message.The table below shows one example how the OCC can be extended also inthis case.

TABLE 2 OCC indicates presence of reserved RE in the subframe forlocalized EPDCCH Antenna port ^(p) [w _(p)(0) w _(p)(1) [w _(p)(0) w_(p)(1) w _(p)(2) w _(p)(3)] w _(p)(2) w _(p)(3)] Reserved RE present NoYes 107 [+1 +1 +1 +1] [+1 +1 −1 −1] 108 [+1 −1 +1 −1] [+1 −1 −1 +1] 109[+1 +1 +1 +1] [+1 +1 −1 −1] 110 [+1 −1 +1 −1] [+1 −1 −1 +1]

In this regard, FIG. 11 illustrates the operation of the base station 14and the wireless device 18 according to some embodiments in which thebase station 14 transmits a downlink transmission (e.g., an EPDCCHtransmission or a PDSCH transmission) to the wireless device 18 alongwith an OCC indicator that indicates whether reserved REs are present,as described above. As illustrated, the base station 14 transmits anEPDCCH or PDSCH transmission to the wireless device 18 in a subframealong with an OCC indicator that indicates whether reserved REs arepresent (step 200). In particular, in some embodiments, the OCCindicator indicates whether reserved REs are present in the subframe inwhich the EPDCCH or PDSCH transmission is transmitted. As discussedabove, in some embodiments, the OCC indicator indicates only whether thereserved REs are present. In other embodiments, the OCC indicator alsoindicates the locations, or positions, of the reserved REs (e.g.,indicates which of multiple predefined sets of reserved REs arepresent). In some embodiments, the OCC indicator is the OCC used forDMRS transmitted in the PRB(s) on which the EPDCCH or PDSCH transmissionis transmitted. In some other embodiments, the OCC indicator is the OCCused for port 7 for the PDSCH transmission. Note, however, that the OCCindicator may be transmitted according to any of the embodimentsdescribed above.

The wireless device 18 detects the OCC indicator (step 202). Forexample, if the OCC indicator is the OCC used for the DMRS transmittedwithin the PRB(s) used for the EPDCCH transmission, then the wirelessdevice 18 detects the OCC used for the DMRS. Based on the OCC indicator,the wireless device 18 determines whether reserved REs are present. Thewireless device 18 then receives (i.e., attempts to receive) the EPDCCHor PDSCH transmission according to the detected OCC indicator (step204). For example, if reserved REs are present and the base station 14performs rate-matching of the downlink transmission around the reservedREs, then the wireless device 18 de-maps REs used for the downlinktransmission from the received PRB(s) and avoids demapping symbols fromreserved REs. As another example, if reserved REs are present and thebase station 14 punctures the downlink transmission at the positions ofthe reserved REs, then the wireless device 18 ignores the reserved REsduring decoding of the downlink transmission as the reserved REs willnot include useful information for decoding the downlink transmission.Notably, the process of FIG. 11 is dynamic in that the OCC indicator isprovided in the respective subframes such that the wireless device 18 isenabled to dynamically detect the presence of reserved REs withinsubframes via the respective OCC indicator.

FIG. 12 is flow chart that illustrates the operation of the wirelessdevice 18 with respect to receiving and using an OCC indicator (alsoreferred to herein as an OCC-based indication) according to someembodiments of the present disclosure. As illustrated, the processbegins with subrame i (step 300). The wireless device 18 detects the OCCindicator in subframe i (step 302). Based on the detected OCC indicator,the wireless device 18 determines whether reserved REs are present insubframe i (step 304). In particular, the wireless device 18 detects theOCC indicator within PRB(s) in which the wireless device 18 is toattempt downlink reception (of an EPDCCH or PDSCH transmission) and,based on the detected OCC indicator, determines whether reserved REs arepresent in those PRB(s). If reserved REs are present, the wirelessdevice 18 attempts reception of a downlink physical channel (i.e., adownlink transmission) (e.g., an EPDCCH or PDSCH) assuming reserved REsare present (step 306). Otherwise, if the OCC indicator detectionindicates that reserved REs are not present, the wireless device 18attempts reception of the downlink physical channel assuming thatreserved REs are not present (step 308). The subframe index i is thenincremented (step 310), and the process returns to step 300 and isrepeated for the next subframe. In this manner, the OCC-based indicationscheme is dynamic.

The new signaling described herein may be utilized in various manners.In some embodiments, the new signaling is utilized in a network,particularly for MTC or coverage extension applications. Both wirelessdevice 18 (e.g., UE) and base station 14 (e.g., eNB) implementations areconsidered. For the following discussion, the base station 14 isspecifically an eNB, and the wireless device 18 is specifically a UE;however, the following embodiments are not limited thereto.

In some embodiments, the eNB rate matches the transmitted message aroundthe reserved RE. So, by detecting the indication correctly in thereceiving UE, the UE can de-map the message from the correct set of REs.This has the advantage that “aware UEs” that have already managed toreceive the dedicated RRC configuration of reserved REs (e.g., CSI-RSconfiguration) can receive the same PDSCH/EPDCCH message as those“unaware UEs” that have not received this RRC configuration yet. This isuseful for broadcast messages such as system information, or messagesfor which the receiver is temporarily unknown to the transmitter, suchas the RAR. Hence, the message is in the transmission mapped to the sameset of REs in the subframe, avoiding the reserved REs, irrespective ofwhether the receiving UE is aware of the reserved REs or not. The “awareUE” can then directly use the alternative OCC when performing channelestimation in subframes where it knows there are CSI-RSs present. Hence,there is no need for the aware UE to perform the OCC detection.

In some other embodiments, the eNB punctures the message by CSI-RS. TheUE may then, by detection using DMRS according to embodiments of thedisclosure, understand that there is no useful information (no message)in these reserved RSs as they contain other information such as CSI-RSfor other UEs, and can thus ignore these REs. This will improve thereception performance since garbage samples are not introduced into thedecoder. The UE may in this case set the soft bit information of themessage corresponding to these reserved REs to zero. An aware UE alsoneeds to avoid the samples from these reserved REs, but the aware UEneed not perform the detection step as it can directly use the correctDMRS/OCC.

A benefit of this puncturing embodiment, as opposed to the rate matchingembodiment, is increased robustness, since if the detection fails in theUE, the message may still be decoded since the UE always assumes thecorrect number of encoded bits. In this case, the correct number ofencoded bits is the same irrespective of whether the reserved REs arepresent or not in the subframe. If the receiver does not know the totalnumber of encoded bits, the message is usually impossible to decode.

In some further embodiments, the detection is performed in multiplesubframes in a repetition window, used for coverage enhancements in LTE.Hence, the UE may detect reserved REs in some subframes and “clean”subframes as well within one PDSCH/EPDCCH repetition window. If thepuncturing approach is used, then the UE may use energy aggregation fora given RE across the subframes. In an aggregation bundle that carries adownlink transmission (either control or data), the UE then shouldignore reserved REs from subframes where an indication of reserved REshas been detected.

Regarding the impact to EPDCCH construction, for eCCE mapping toconstruct EPDCCH, the presence or absence of CSI-RS is taken intoaccount in the legacy system, since the UE-specific RRC signal carryingCSI-RS configuration has been received. Moreover, rate matching isalways applied in constructing the EPDCCH. For an MTC UE, EPDCCH may besent prior to receiving UE-specific RRC signaling. This includes, forexample, EPDCCH common search space, EPDCCHs that are used to schedulePDSCH carrying MTC-SIB, paging, or random access responses. Compared tolegacy EPDCCH, EPDCCHs that are receivable prior to the UE-specific RRCsignal are different in terms of their construction.

Puncturing vs rate matching: EPDCCHs prior to a UE-specific RRC signalmay need to use puncturing so that the EPDCCH is receivable even if theCSI-RS configuration information is not detected or detectedincorrectly.

Imprecise CSI-RS configuration information: For EPDCCHs prior to aUE-specific RRC signal, the UE may only have imprecise CSI-RSconfiguration information, even if such configuration has been provided.Hence the eNB needs to take this into account in EPDCCH transmission,for example, by providing a higher aggregation level or more repetitionacross subframes.

In the embodiments of FIGS. 11 and 12, the presence of reserved REs wassignaled via an OCC indicator. However, in other embodiments, thepresence of reserved REs is signaled via broadcast signaling. Morespecifically, for SIB, RAR, paging, and EPDCCH common search space, thesystem information broadcast message may broadcast the CSI-RS occupationinformation (reserved RE) so that the common messages may be receivedwhile taking into account the presence of CSI-RS. This is alsoapplicable to an EPDCCH UE-specific search space, before the RRCconfiguration of CSI-RS is received.

Since MTC-SIB2 (and several other MTC-SIBs) needs to be receivable byMTC UEs in RRC_IDLE, the MTC-SIBs have to be receivable by UEs that donot have RRC connection yet, in a state where the CSI-RS configurationis unknown. Thus, the CSI-RS configuration has to be broadcast so thatUEs in RRC_IDLE state can also receive the information.

Note that the downlink messages designated to MTC UE reception, e.g.,MTC-SIB, RAR, paging, are different from those not designated to MTC UEreception. For the generic SIB/RAR/paging, they need to be receivable byall legacy UEs. However, for those designed for MTC UEs, they only needto be receivable by Rel-13 (and later) UEs. Thus, backwardscompatibility is no longer a requirement. Thus, the presence of reservedREs can be signaled and taken into account.

Regardless of which broadcast signal is used to carry the CSI-RSconfiguration, all downlink transmissions after the broadcast signal canutilize the CSI-RS configuration, but those before it are not able toutilize the CSI-RS configuration. For all of the downlinktransmission(s) before the given broadcast signal, the UE assumes thatCSI-RS are not present. For example, if MTC-SIB2 is designated to carrythe CSI-RS configuration, then for receiving MTC-SIB1 and MTC-SIB2, theUE assumes that CSI-RS is not present. But the UE can account for theCSI-RS in receiving MTC-SIB3/4/ . . . , RAR, paging, and EPDCCH.

In some embodiments, CSI-RS configuration is carried in (i.e., includedin) MTC-SIB1. Scheduling of MTC-SIB2/3/ . . . is via MTC-SIB1 or EPDCCH.In this case, MTC-SIB1 can provide a rough level of CSI-RSconfiguration. For example, subframe configuration of CSI-RS can beprovided while within a subframe containing CSI-RS, and it is assumedthat the maximum of 40 REs are reserved. The eNB punctures REs taken byCSI-RS when transmitting MTC-SIB1. When transmitting MTC-SIB2/3/ . . . ,the eNB can take into account the CSI-RS configuration provided byMTC-SIB1. Using puncturing as an example, when receiving MTC-SIB2/3/ . .. (and its associated EPDCCH, if defined), the UE receiver knows topuncture the CSI-RS REs notified by the MTC-SIB1 in the decodingprocess. A similar process applies if rate matching is used instead ofpuncturing.

In contrast, if the MTC-SIB1 does not provide CSI-RS configuration andthe eNB simply punctures REs taken by CSI-RS, the UE receiver does notknow to puncture any CSI-RS REs when receiving MTC-SIB2/3/ . . . . TheUE assumes that CSI-RS are not present in the subframe when receivingMTC-SIB2/3/ . . . . This degrades the UE reception quality. Thus, theeNB needs to use a lower Modulation and Coding Scheme (MCS) tocompensate.

Since MTC-SIB1 is sent more frequently than MTC-SIB2/3/ . . . , theamount of information sent in MTC-SIB1 is limited. Thus, only fairlyrough CSI-RS configuration information can be carried by MTC-SIB1, forexample only time domain information in terms of subframe index, but notthe pattern of reserved REs within a subframe.

In some other embodiments, CSI-RS configuration is carried in a MTC-SIBlater than MTC-SIB1. In this case, later MTC-SIB (e.g., MTC-SIB2) canprovide a more detailed level of CSI-RS configuration. For example, themore detailed level of CSI-RS configuration may include not only timedomain information in terms of subframe indices, but also the pattern ofreserved REs within a subframe. The later MTC-SIB is allowed to carrymore bits since later MTC-SIBs are sent less frequently than MTC-SIB,thus incurring relatively lower overhead.

Using puncturing as an example, in some embodiments, the eNB puncturesREs taken by CSI-RS. When receiving various types of downlink messages,the UE receiver knows to puncture the CSI-RS REs notified by theMTC-SIB2 in the decoding process. The downlink message types include:MTC-SIB3/ . . . , RAR, paging, and the EPDCCH before receiving CSI-RSconfiguration via RRC signaling. A similar technique applies if ratematching is used instead of puncturing.

Compared to using MTC-SIB1, using MTC-SIB2 (for example) to carry theCSI-RS configuration information means that PDSCH carrying MTC-SIB2itself cannot utilize the CSI-RS information. Hence, PDSCH carryingMTC-SIB2 may need to be transmitted with stronger robustness, forexample, by assigning lower modulation and coding rate and/or assigningmore repetitions in time.

FIG. 13 illustrates the operation of the base station 14 and thewireless device 18 to provide and utilize broadcast signaling forindicating the presence of reserved REs according to some embodiments ofthe present disclosure. As described above, the base station 14 (e.g.,eNB) broadcasts a (first) indicator of the presence of reserved REs(step 400). This broadcast indicator includes, in some embodiments, timedomain information regarding the presence of reserved REs (e.g.,information that indicates which subframes include reserved REs). Inaddition, the broadcast indicator may further include more detailedinformation about the reserved REs (e.g., information that indicateswhich REs are reserved REs within the subframes that include reservedREs). As discussed above, in some embodiments, the broadcast indicatoris included in a Master Information Block (MIB) (e.g., a MTC MIB) or aSIB (e.g., a MTC SIB such as, e.g., MTC-SIB2).

The wireless device 18 receives the broadcast indicator (step 402). Atsome point, the base station 14 transmits a downlink transmission (i.e.,a downlink physical channel such as EPDCCH or PDSCH) to the wirelessdevice 18 (step 404). The wireless device 18 receives (or attempts toreceive) the downlink transmission according to the received broadcastindicator, as described above (step 406).

In some embodiments, the first indicator may be basic information (e.g.,time domain information) regarding reserved REs provided via a MIB(e.g., MTC MIB), and a second indicator may subsequently be receivedthat includes more detailed information regarding the reserved REs(e.g., information that indicates which REs within a subframe(s) arereserved REs). In this regard, in some embodiments (i.e., optionally),the base station 14 further broadcasts a second indicator of thepresence of reserved REs that is more detailed than the first indicator(step 408). The second indicator may be included in a SIB (e.g.,MTC-SIB2 or later). The wireless device 18 receives the second indicator(step 410). At some point, the base station 14 transmits a downlinktransmission (i.e., a downlink physical channel such as EPDCCH or PDSCH)to the wireless device 18 (step 412). The wireless device 18 receives(or attempts to receive) the downlink transmission according to thefirst and second indicators, as described above (step 414).

FIG. 14 is a flow chart that illustrates the operation of the wirelessdevice 18 in more detail according to some embodiments of the presentdisclosure. In this example, it is assumed that the configuration ofreserved REs is sent via MTC-SIB1. As illustrated, the wireless device18 receives and stores a configuration of reserved REs from MTC-SIB1(step 500). For subframe i (step 502), the wireless device 18 looks upthe configuration of reserved REs for subframe i from the storedconfiguration information (step 504). The wireless device 18 determineswhether reserved REs are present for subframe i based on the storedconfiguration information (step 506). If reserved REs are present insubframe i (and potentially if reserved REs are present in the PRB(s) onwhich downlink reception is to be attempted), the wireless device 18attempts reception of a downlink physical channel (i.e., a downlinktransmission) (e.g., an EPDCCH or PDSCH) assuming reserved REs arepresent (step 508). Otherwise, if reserved REs are not present, thewireless device 18 attempts reception of the downlink physical channelassuming that reserved REs are not present (step 510). The subframeindex i is then incremented (step 512), and the process returns to step502 and is repeated for the next subframe.

Although the described solutions may be implemented in any appropriatetype of telecommunication system supporting any suitable communicationstandards and using any suitable components, particular embodiments ofthe described solutions may be implemented in an LTE network, such asthat illustrated in FIG. 9. As described above, the example network mayinclude one or more instances of wireless (communication) devices (e.g.,conventional UEs, MTC/Machine-to-Machine (M2M) UEs, etc.) and one ormore radio access nodes (e.g., eNBs or other base stations) capable ofcommunicating with these wireless communication devices along with anyadditional elements suitable to support communication between wirelesscommunication devices or between a wireless communication device andanother communication device (such as a landline telephone).

Similarly, although the illustrated base station 14 (or more generallyradio access node) may represent network nodes that include any suitablecombination of hardware and/or software, these nodes may, in particularembodiments, represent devices such as the example radio access nodeillustrated in greater detail by FIG. 15. As shown in FIG. 15, theexample base station 14 (or more generally radio access node) includeshardware components such as a processor 28 (e.g., one or more of aCentral Processing Unit (CPU), Application Specific Integrated Circuit(ASIC), Field Programmable Gate Array (FPGA), and/or the like), memory30, a network interface 32, and a transceiver 34 (which may includetransmitters and/or receivers), and an antenna(s) (not labelled). Inparticular embodiments, some or all of the functionality described aboveas being provided by a base station 14 or eNB and/or any other type ofnetwork node may be provided by the processor 28 executing instructionsstored on a computer-readable medium, such as the memory 30. Alternativeembodiments of the base station 14 (or radio access node) may includeadditional components responsible for providing additionalfunctionality, including any of the functionality identified aboveand/or any functionality necessary to support the solution describedabove.

In some embodiments, the base station 14 (e.g., eNB) can be configuredto transmit the system information broadcast message, which maybroadcast the CSI-RS occupation information (reserved RE) so that thecommon messages may be received while taking into account the presenceof CSI-RS. This is also applicable to EPDCCH UE-specific search space,before the RRC configuration of CSI-RS is received. The base station 14(e.g., eNB) can additionally or alternatively transmit an OCC indictorthat indicates the presence of reserved REs for either a distributed orlocalized physical control channel (e.g., EPDCCH) or a physical sharedchannel (e.g., PDSCH), as described above.

FIG. 16 is a schematic block diagram that illustrates a virtualizedembodiment of the base station 14 according to some embodiments of thepresent disclosure. This discussion is equally applicable to other typesof radio access nodes. Further, other types of network nodes may havesimilar architectures (particularly with respect to includingprocessor(s), memory, and a network interface).

As used herein, a “virtualized” radio access node is a radio access nodein which at least a portion of the functionality of the base station 14is implemented as a virtual component (e.g., via a virtual machine(s)executing on a physical processing node(s) in a network(s)). Asillustrated, the base station 14 includes a processing node 36 thatincludes one or more processors 38 (e.g., CPUs, ASICs, FPGAs, and/or thelike), memory 40, and a network interface 42 as well as one or moreradio units 44 that each includes one or more transmitters 46 and one ormore receivers 48 coupled to one or more antennas 50. The processingnode 36 is connected to the radio unit(s) 44 via, for example, anoptical cable or the like. The processing node 36 is connected to one ormore processing nodes 54 coupled to or included as part of a network(s)52 via the network interface 42. Each processing node 54 includes one ormore processors 56 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory58, and a network interface 60. Note that the processor(s) 38, thememory 40, and the network interface 42 of FIG. 16 correspond to theprocessor 28, the memory 30, and the network interface 32 of FIG. 15.Similarly, the transmitter(s) 46 and the receiver(s) 48 of FIG. 16correspond to the transceiver 34 of FIG. 15.

In this example, functions 62 of the base station 14 described hereinare implemented at the one or more processing nodes 54 or distributedacross the processing node 36 and the one or more processing nodes 54 inany desired manner. In some particular embodiments, some or all of thefunctions 62 of the base station 14 described herein are implemented asvirtual components executed by one or more virtual machines implementedin a virtual environment(s) hosted by the processing node(s) 54. As willbe appreciated by one of ordinary skill in the art, additional signalingor communication between the processing node(s) 54 and the processingnode 36 is used in order to carry out at least some of the desiredfunctions such as, for example, transmitting the grant and/ortransmitting the indication of the carrier mode of at least one carrier.Notably, in some embodiments, the processing node 36 may not beincluded, in which case the radio unit(s) 44 communicate directly withthe processing node(s) 54 via an appropriate network interface(s).

FIG. 17 illustrates the base station 14 (or more generally radio accessnode) according to some other embodiments of the present disclosure. Asillustrated, the base station 14 includes one or more modules 64, eachof which is implemented in software. For example, the base station 14may include a reserved RE indicator transmission module that operates totransmit, e.g., either an OCC indicator or a broadcast indicator, asdescribed above, via an associated transmitter(s) (not shown) of thebase station 14. The base station 14 also includes a physical channeltransmission module that operates to transmit a physical channel (e.g.,an EPDCCH or a PDSCH), as described above, via an associatedtransmitter(s) (not shown) of the base station 14.

In some embodiments, a computer program including instructions which,when executed by at least one processor, causes the at least oneprocessor to carry out the functionality of base station 14 or eNBaccording to any of the embodiments described herein is provided. Insome embodiments, a carrier containing the aforementioned computerprogram product is provided. The carrier is one of an electronic signal,an optical signal, a radio signal, or a computer readable storage medium(e.g., a non-transitory computer readable medium such as the memory 30).

Although the illustrated wireless device 18 may represent communicationdevices that include any suitable combination of hardware and/orsoftware, these wireless devices 18 may, in particular embodiments,represent devices such as the example wireless device 18 (e.g., UE)illustrated in greater detail by FIG. 18. As shown in FIG. 18, theexample wireless device 18 includes a processor 66 (e.g., one or more ofa CPU, ASIC, FPGA, and/or the like), memory 68, a transceiver 70 (whichincludes a transmitter 72 and a receiver 74), and an antenna(s) 76. Inparticular embodiments, some or all of the functionality described aboveas being provided by the wireless device 18, UEs, MTC, or M2M devices,and/or any other types of wireless devices may be provided by theprocessor 66 executing instructions stored on a computer-readablemedium, such as the memory 68 shown in FIG. 18. Alternative embodimentsof the wireless device 18 may include additional components beyond thoseshown in FIG. 18 that may be responsible for providing certain aspectsof the device's functionality, including any of the functionalitydescribed above and/or any functionality necessary to support thesolution described above.

As described above, the wireless device 18 (e.g., UE) can includestructural elements, such as processor circuitry, transceiver circuitry,memory circuitry, and other hardware components used to carry out theembodiments described herein. The wireless device 18 (e.g., UE) can alsoinclude functional modules 78, as illustrated in FIG. 19. For example,the wireless device 18 may include a receiver module for receivinginformation (e.g., an OCC indicator or a broadcast indicator, asdescribed above) about the reserved REs, a module for determiningwhether a subframe includes reserved REs based on the receivedinformation/indicator, and a module for receiving (or attempting toreceive) a physical channel (e.g., EPDCCH or PDSCH) according to whetherreserved REs are determined to be present, as described above.

The following acronyms are used throughout this disclosure.

-   -   3GPP Third Generation Partnership Project    -   5G Fifth Generation    -   ASIC Application Specific Integrated Circuit    -   CN Core Network    -   CP Cyclic Prefix    -   CPU Central Processing Unit    -   CSI-RS Channel State Information Reference Signal    -   DCI Downlink Control Information    -   DMRS Demodulation Reference Signal    -   eCCE Enhanced Control Channel Element    -   eNB Enhanced or Evolved Node B    -   EPDCCH Enhanced Physical Downlink Control Channel    -   eREG Enhanced Resource Element Group    -   FPGA Field Programmable Gate Array    -   LTE Long Term Evolution    -   M2M Machine-to-Machine    -   MBMS Multimedia Broadcast/Multicast Service    -   MCS Modulation and Coding Scheme    -   MHz Megahertz    -   MIB Master Information Block    -   MME Mobility Management Entity    -   ms Millisecond    -   MTC Machine Type Communication    -   OCC Orthogonal Cover Code    -   OFDM Orthogonal Frequency Division Multiplexing    -   PDCCH Physical Downlink Control Channel    -   PDN Packet Data Network    -   PDSCH Physical Downlink Shared Channel    -   P-GW Packet Data Network Gateway    -   PRB Physical Resource Block    -   PSM Power Saving Mode    -   RAN Radio Access Network    -   RAR Random Access Response    -   RB Resource Block    -   RE Resource Element    -   Rel-8 Release 8    -   Rel-11 Release 11    -   Rel-12 Release 12    -   Rel-13 Release 13    -   RF Radio Frequency    -   RRC Radio Resource Control    -   RS Reference Signal    -   SCEF Service Capability Exposure Function    -   S-GW Serving Gateway    -   SIB Secondary Information Block    -   SIM Subscriber Identification Module    -   TDD Time Division Duplexing    -   TS Technical Specification    -   UE User Equipment

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. A radio access node for a cellular communicationsnetwork, comprising: a transceiver; a processor; and memory storinginstructions executable by the processor whereby the radio access nodeis operable to: transmit, via the transceiver, a downlink transmissionto a wireless device using one or more Physical Resource Blocks, PRBs,that comprise reserved Resource Elements, REs, by puncturing thedownlink transmission at positions of the reserved REs, the downlinktransmission being a Physical Downlink Shared Channel, PDSCH,transmission, wherein the radio access node is further operable totransmit the downlink transmission at a reduced code rate whenpuncturing of the downlink transmission at positions of the reserved REshas occurred.
 2. The radio access node of claim 1 wherein the reservedREs are REs utilized for one or more Channel State Information ReferenceSignals, CSI-RSs.
 3. A method of operation of a radio access node in acellular communications network, comprising: transmitting a downlinktransmission to a wireless device using one or more Physical ResourceBlocks, PRBs, that comprise reserved Resource Elements, REs, bypuncturing the downlink transmission at positions of the reserved REs,the downlink transmission being a Physical Downlink Shared Channel,PDSCH, transmission, wherein the transmitting the downlink transmissionto the wireless device comprises transmitting the downlink transmissionat a reduced code rate when puncturing of the downlink transmission atpositions of the reserved REs has occurred.
 4. The method of claim 3wherein the reserved REs are REs utilized for one or more Channel StateInformation Reference Signals, CSI-RSs.
 5. A non-transitorycomputer-readable medium storing software instructions that whenexecuted by one or more processors of a radio access node cause theradio access node to: transmit a downlink transmission to a wirelessdevice using one or more Physical Resource Blocks, PRBs, that comprisereserved Resource Elements, REs, by puncturing the downlink transmissionat positions of the reserved REs, the downlink transmission being aPhysical Downlink Shared Channel, PDSCH, transmission, wherein the radioaccess node is caused to transmit the downlink transmission at a reducedcode rate when puncturing of the downlink transmission at positions ofthe reserved REs has occurred.
 6. A wireless device enabled to operatein a cellular communications network, comprising: a transceiver; aprocessor; and memory storing instructions executable by the processorwhereby the wireless device is operable to: receive, via thetransceiver, a downlink transmission from a radio access node on one ormore Physical Resource Blocks, PRBs, based on an assumption by thewireless device that the downlink transmission on the one or more PRBsis punctured by reserved Resource Elements, REs, if any, the downlinktransmission being a Physical Downlink Shared Channel, PDSCH,transmission, wherein the wireless device is further operable to receivethe downlink transmission from the radio access node at a reduced coderate when puncturing of the downlink transmission at positions of thereserved REs has occurred.
 7. The wireless device of claim 6 wherein thereserved REs are REs utilized for one or more Channel State InformationReference Signals, CSI-RSs.
 8. A method of operation of a wirelessdevice in a cellular communications network, comprising: receiving adownlink transmission from a radio access node on one or more PhysicalResource Blocks, PRBs, based on an assumption by the wireless devicethat the downlink transmission on the one or more PRBs is punctured byreserved Resource Elements, REs, if any, the downlink transmission beinga Physical Downlink Shared Channel, PDSCH, transmission, whereinreceiving the downlink transmission from the radio access node furthercomprises receiving the downlink transmission from the radio access nodeat a reduced code rate when puncturing of the downlink transmission atpositions of the reserved REs has occurred.
 9. The method of claim 8wherein the reserved REs are REs utilized for one or more Channel StateInformation Reference Signals, CSI-RSs.
 10. A non-transitorycomputer-readable medium storing software instructions that whenexecuted by one or more processors of a wireless device cause thewireless device to: receive a downlink transmission from a radio accessnode on one or more Physical Resource Blocks, PRBs, based on anassumption by the wireless device that the downlink transmission on theone or more PRBs are punctured by reserved Resource Elements, REs, ifany, the downlink transmission being a Physical Downlink Shared Channel,PDSCH, transmission, wherein the wireless device is caused to receivethe downlink transmission from the radio access node at a reduced coderate when puncturing of the downlink transmission at positions of thereserved REs has occurred.
 11. A method of operation of a wirelessdevice in a cellular communications network, comprising: obtaining anindicator that is indicative of whether reserved Resource Elements, REs,are present in a subframe in which a downlink transmission istransmitted from a radio access node to the wireless device, thedownlink transmission being one of a group consisting of: an EnhancedPhysical Downlink Control Channel, EPDCCH, transmission or a PhysicalDownlink Shared Channel, PDSCH, transmission; determining whetherreserved REs are present in the subframe based on the indicator; andupon determining that reserved REs are present in the subframe,attempting reception of the downlink transmission based on an assumptionthat reserved REs are present in the subframe.
 12. The method of claim11 further comprising, upon determining that reserved REs are notpresent in the subframe, attempting reception of the downlinktransmission based on an assumption that reserved REs are not present inthe subframe.
 13. The method of claim 11 wherein the downlinktransmission is an EPDCCH transmission.
 14. The method of claim 13wherein the reserved REs are REs utilized for one or more Channel StateInformation Reference Signals, CSI-RSs.
 15. The method of claim 11wherein the downlink transmission is a PDSCH transmission.
 16. Themethod of claim 15 wherein the reserved REs are REs utilized for one ormore Channel State Information Reference Signals, CSI-RSs.
 17. Themethod of claim 11 wherein obtaining the indicator comprises detectingan Orthogonal Cover Code, OCC, indicator in the subframe that isindicative of whether reserved REs are present in the subframe.
 18. Themethod of claim 17 wherein the OCC indicator is an OCC utilized for aDemodulation Reference Signal, DMRS, antenna port within one or morePhysical Resource Blocks (PRBs).
 19. The method of claim 17 wherein theOCC indicator is further indicative of which of a plurality ofpredefined sets of reserved REs is present in the subframe.
 20. Themethod of claim 17 wherein positions of the reserved REs within thesubframe are predefined.
 21. The method of claim 11 wherein obtainingthe indicator comprises receiving and storing a configuration ofreserved REs in multiple subframes, including the subframe, fromreceived system information, the configuration of reserved REs in themultiple subframes comprising the indicator that is indicative ofwhether reserved REs are present in the subframe.
 22. The method ofclaim 21 wherein the wireless device is a Machine Type Communication,MTC, device, and the received system information is a MTC MasterInformation Block, MTC-MIB.
 23. The method of claim 21 wherein thewireless device is a Machine Type Communication, MTC, device, and thereceived system information is a MTC Secondary Information Block,MTC-SIB.
 24. The method of claim 11 wherein attempting reception of thedownlink transmission based on an assumption that reserved REs arepresent in the subframe comprises de-mapping a plurality of REscorresponding to the downlink transmission from one or more PhysicalResource Blocks, PRBs, in the subframe.
 25. The method of claim 11wherein attempting reception of the downlink transmission based on anassumption that reserved REs are present in the subframe comprisesignoring the reserved REs during reception of the downlink transmission.26. A wireless device enabled to operate in a cellular communicationsnetwork, comprising: a transceiver; a processor; and memory storinginstructions executable by the processor whereby the wireless device isoperable to: obtain an indicator that is indicative of whether reservedResource Elements, REs, are present in a subframe in which a downlinktransmission is transmitted from a radio access node to the wirelessdevice, the downlink transmission being one of a group consisting of: anEnhanced Physical Downlink Control Channel, EPDCCH, transmission or aPhysical Downlink Shared Channel, PDSCH, transmission; determine whetherreserved REs are present in the subframe based on the indicator; andupon determining that reserved REs are present in the subframe, attemptreception of the downlink transmission based on an assumption thatreserved REs are present in the subframe.
 27. The wireless device ofclaim 26 wherein, in order to obtain the indicator, the wireless deviceis further operable to detect an orthogonal cover code, OCC, indicatorin the subframe that is indicative of whether reserved REs are presentin the subframe.
 28. The wireless device of claim 26 wherein, in orderto obtain the indicator, the wireless device is further operable toreceive and store a configuration of reserved REs in multiple subframes,including the subframe, from received system information, theconfiguration of reserved REs in the multiple subframes comprising theindicator that is indicative of whether reserved REs are present in thesubframe.
 29. A non-transitory computer-readable medium storing softwareinstructions that when executed by one or more processors of a wirelessdevice cause the wireless device to: obtain an indicator that isindicative of whether reserved Resource Elements, REs, are present in asubframe in which a downlink transmission is transmitted from a radioaccess node to the wireless device, the downlink transmission being oneof a group consisting of: an Enhanced Physical Downlink Control Channel,EPDCCH, transmission or a Physical Downlink Shared Channel, PDSCH,transmission; determine whether reserved REs are present in the subframebased on the indicator; and upon determining that reserved REs arepresent in the subframe, attempt reception of the downlink transmissionbased on an assumption that reserved REs are present in the subframe.30. The radio access node of claim 1 wherein the radio access node isoperable to repeat the downlink transmission to the wireless device apredetermined number of times when puncturing of the downlinktransmission at positions of the reserved REs has occurred.
 31. Themethod of claim 3 further comprising repeating the transmission of thedownlink transmission to the wireless device a predetermined number oftimes when puncturing of the downlink transmission at positions of thereserved REs has occurred.
 32. The wireless device of claim 6 whereinthe wireless device is further operable to receive multiple repetitionsof the downlink transmission from the radio access node when puncturingof the downlink transmission at positions of the reserved REs hasoccurred.
 33. The method of claim 8 further comprising receiving thedownlink transmission from the radio access node a predetermined numberof times when puncturing of the downlink transmission at positions ofthe reserved REs has occurred.